NOW, I don’t know much about science but I know a really big greenhouse when I see one – and this is one really big greenhouse.

The size of a football pitch and standing in splendid isolation in stunning Icelandic countryside, this is not just any greenhouse.

It is one of three where barley is grown in 2000-year-old volcanic pumice, barley used in what has become one of the most ­spectacular cosmetic success stories in ­decades.

Some fans call it a miracle cream. Some call it the elixir of youth. It is the £125-a-time Sif Cosmetics’ Bioeffect EGF Serum.

It has caused a huge stir since it was quietly dropped into the market in 2010. Relying on word of mouth in an industry dominated by glossy ­advertising, the Icelandic firm’s product has won ­thousands of fans, including celebrities such as actress Uma Thurman.

In Iceland, a third of women over 30 use it while it is now being stocked in the world’s most famous stores.

To give you an idea, it was the first product to top British Airways’ onflight sales that wasn’t cigarettes or alcohol.

So, invited to see where it was made, I was on a flight to Reykjavik before you could say pickled herring. Let me just say that, at school, science was never my strong subject – knowing the ­difference between a test tube and a Bunsen burner was as far as I went. But as the first Scottish beauty journalist to be granted an access-all-areas trip to the Reykjavik plant, I was fascinated.

The secret is the key ingredient EGF or Epidermal Growth Factor. This naturally occurring skin protein acts as a cellular messenger to kickstart the production of collagen, while supporting the skin’s own repair process.

Well, that’s what they told me as I nodded and pretended to understand the appliance of science.

Actress Uma Thurman is a big fan of the cream (Photo: Regis Duvignau)

But while the science might baffle me, the results don’t – and fans around the world are swearing by the little clear bottle’s magic formula that uses just nine ingredients.

So pure, according to the firm, that you could safely drink it.

There were times in my tour when snippets of information whooshed up and straight over my head. So I’ll keep it simple. This must-have product all started by copying the human EGF gene into barley seeds.

For me, seeing is believing but I could still hardly believe the ­greenhouse. This giant incubator – lit 24 hours a day – sits ­illuminating the sky as bright as the northern lights.

It is green-powered by geothermal energy from hot springs and plays home to the first part of the product process.

It is here that thousands of barley shoots are grown.

A partnership between nature and science, the barley is grown in conditions geared to exploit the perfect climatic conditions and resources of the country.

The readily available volcanic pumice is where the seeds are planted and watered with pure ­Icelandic spring water before the EGF is extracted.

EGF can be grown in different environments but this is the only company who do it naturally.

Bjorn Orvar, the chief executive at Sif, says the product simply could not be produced anywhere else.

He said: “Every aspect of the ­process is made in Iceland. From the cultivation to the formulation and even the packaging, no part is ­outsourced.”

Proud of how his product’s ­popularity has been built without advertising, Bjorn said the secret is how the EGF can “bluff” skin into thinking it’s younger.

He said: “When we used the ­product on the skin of a 52-year-old, we were able to reduce its age by more than 10 years, giving it the density of a 40-year-old after just four weeks.”

The product has now won a host of awards and the backing of experts such as Dr Ronald Moy, professor of dermatology at the University of California and former president of the American Academy of ­Dermatology.

He said the results were the best he has witnessed ­during his 30 years of practice. Okay, I’m thinking, this guy has some serious clout so this has to be good.

My first glimpse of it was on a flight to Bermuda. After welcome drinks, my first port of call was the product page in the in-flight magazine and it was here that I noticed Bioeffect.

Its sales success on British Airways long-haul flights last year meant it was introduced on short-haul routes too in January and, in the first quarter, became BA’s top-selling product.

At £125 for 15ml, it is not the cheapest product on the market but, compared to other high-performance items such as Dior’s L’Or De Vie Le Serum coming in at £300 and La Prairie’s Cellular Radiance Concentrate Pure Gold at £418, it almost looks like a bargain buy.

Also, bear in mind that it’s claimed to be so potent that no other ­products are needed, streamlining your beauty bag and your spend.